Structural members for infrastructure, such as beams and columns, are typically made from steel and/or concrete. However, over the years, both have shown several drawbacks. For instance, corrosion is a problem for steel structural supports especially in corrosive environments. Concrete structural members are also subjected to deterioration of their long-term durability and their structural durability. Permeability of the exposed concrete by water can cause the concrete to deteriorate over time. For example, in northern climate areas that are subjected to the changeable weather conditions due to winter and summer, moisture trapped and frozen in concrete during the winter can expand during summer and cracks the concrete structural members. Furthermore, corrosion is known to occur to the reinforcing steel bars used inside reinforced concrete (RC) structural members.
Over the last years, the use of an external tube, as an outer shell, filled with concrete has been found to isolate and waterproof exposed concrete structural applications, as well as remove the need for formwork and formwork removal. However, these structural members are typically relatively heavy, which may increase transportation and installation costs substantially.